System formed through package-in-package formation

ABSTRACT

A package includes a first device die, and a second device die bonded to the first device die through hybrid bonding. The second device die is larger than the first device die. A first isolation region encapsulates the first device die therein. The first device die, the second device die, and the first isolation region form parts of a first package. A third device die is bonded to the first package through hybrid bonding. The third device die is larger than the first package. A second isolation region encapsulates the first package therein. The first package, the third device die, and the second isolation region form parts of a second package.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of the following U.S. ProvisionalApplication No. 62/854,401, filed May 30, 2019, and entitled “Systemformed Through Package in Package Formation,” which application ishereby incorporated herein by reference.

BACKGROUND

The packages of integrated circuits are becoming increasing complex,with more device dies packaged in the same package to achieve morefunctions. For example, a package structure has been developed toinclude a plurality of device dies such as processors and memory cubesin the same package. The package structure can include device diesformed using different technologies and have different functions bondedto the same device die, thus forming a system. This may savemanufacturing cost and optimize device performance.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 and 2 illustrate the cross-sectional views of a device wafer anda corresponding device die in accordance with some embodiments.

FIGS. 3 through 22 are cross-sectional views of intermediate stages inthe formation of a package in accordance with some embodiments.

FIGS. 23 through 26 are cross-sectional views of intermediate stages inthe formation of a package in accordance with some embodiments.

FIGS. 27 through 33 illustrate some applications for the packages formedin accordance with some embodiments.

FIG. 34 illustrates a process flow for forming a package in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A package and the method of forming the same are provided in accordancewith some embodiments. The intermediate stages in the formation of thepackage are illustrated in accordance with some embodiments. Somevariations of some embodiments are discussed. Embodiments discussedherein are to provide examples to enable making or using the subjectmatter of this disclosure, and a person having ordinary skill in the artwill readily understand modifications that can be made while remainingwithin contemplated scopes of different embodiments. Throughout thevarious views and illustrative embodiments, like reference numbers areused to designate like elements. Although method embodiments may bediscussed as being performed in a particular order, other methodembodiments may be performed in any logical order.

In accordance with some embodiments of the present disclosure, a packageincludes a plurality of device dies bonded together. The formation ofthe package may include bonding device dies to a wafer to form a firstreconstructed wafer. The first reconstructed wafer is singulated asfirst packages. The first packages are bonded to a second wafer to forma second reconstructed wafer. The second reconstructed wafer issingulated as second packages. Further processes may be performed tofurther incorporating more device dies with the formed packages.

FIG. 1 illustrates a device wafer in accordance with some embodiments.The subsequently used wafers (such as wafers 210 (FIG. 3), 310 (FIG. 9),410 (FIG. 14), and 510 (FIG. 19)) may have similar or same structures asdevice wafer 10, hence the details of the subsequently used wafers arenot discussed in detail, and the details of these wafers may be foundreferring to the discussion of wafer 10. Wafer 10 includes a pluralityof device dies 10′ therein. Device wafer 10 includes substrate 20. Inaccordance with some embodiments, substrate 20 is a semiconductorsubstrate, which may include or be a crystalline silicon substrate,while it may also comprise or be formed of other semiconductor materialssuch as silicon germanium, silicon carbon, or the like. In accordancewith some embodiments, device dies 10′ include active circuits 24, whichinclude active devices such as transistors (not shown) formed at the topsurface of semiconductor substrate 20. Through-vias (sometimes referredto as Through-Substrate Vias (TSVs)) 26 may be formed to extend intosubstrate 20 in accordance with some embodiments. In accordance withalternative embodiments, wafer 10 does not include TSV formed therein.TSVs 26 are also sometimes referred as through-silicon vias when formedin a silicon substrate. Each of TSVs 26 may be encircled by an isolationliner 28, which is formed of a dielectric material such as siliconoxide, silicon nitride, or the like. Isolation liners 28 isolate therespective TSVs 26 from semiconductor substrate 20. TSVs 26 andisolation liners 28 extend from a top surface of semiconductor substrate20 to an intermediate level between the top surface and the bottomsurface of semiconductor substrate 20. In accordance with someembodiments, the top surfaces of TSVs 26 are level with the top surfaceof semiconductor substrate 20. In accordance with alternativeembodiments, TSVs 26 extend into one of dielectric layers 32, and extendfrom a top surface of the corresponding dielectric layer 32 down intosemiconductor substrate 20.

Interconnect structure 30 is formed over semiconductor substrate 20.Interconnect structure 30 may include a plurality of dielectrics layers32. Metal lines 38 and vias 36 are formed in dielectric layers 32, andare electrically connected to TSVs 26 and circuits 24. In accordancewith some embodiments, dielectric layers 32 are formed of silicon oxide,silicon nitride, silicon carbide, silicon oxynitride, combinationsthereof, and/or multi-layers thereof. Dielectric layers 32 may compriseone or more Inter-Metal-Dielectric (IMD) layers formed of low-kdielectric materials having low k values, which may be, for example,lower than about 3.0, or in the range between about 2.5 and about 3.0.

Electrical connectors 42 are formed at the top surface of device dies10′. In accordance with some embodiments, electrical connectors 42comprise metal pillars, metal pads, metal bumps (sometimes referred toas micro-bumps), or the like. The material of electrical connectors 42may include non-solder materials, which may include and may be copper,nickel, aluminum, gold, multi-layers thereof, alloys thereof, or thelike. Electrical connectors 42 may be electrically connected tointegrated circuits 24 through some other conductive features (notshown) including, and not limited, aluminum pads, Post PassivationInterconnect (PPI), or the like, and through metal lines 38 and vias 36.Also, between electrical connectors 42 and metal lines 38, there may bedielectric layers such as low-k dielectric layers, passivation(non-low-k) layers, polymer layers, or the like.

Electrical connectors 42 are in surface dielectric layer 34, and areover and electrically connected to metal pads 40 (such as aluminumcopper pads). In accordance with some embodiments of the presentdisclosure, there may be some Post Passivation Interconnect (PPI)between and interconnecting electrical connectors 42 and thecorresponding metal pads 40. Passivation layers (formed of oxide,nitride, or the like) may be formed to cover some edge portions of metalpads 40. In accordance with some embodiments, polymer layer(s) (such aspolybenzoxazole (PBO), polyimide, or the like) may be formed over themetal pads 40. In accordance with alternative embodiments, nopolymer-containing dielectric layer is formed in wafer 10. In accordancewith some embodiments of the present disclosure, surface dielectriclayer 34 is formed of or comprise a silicon-containing dielectricmaterial, which may or may not include oxygen. For example, surfacedielectric layer 34 may comprise silicon oxide, silicon nitride, siliconoxynitride, or the like.

Throughout the description, the side of semiconductor substrate 20having active circuits 24 and interconnect structure 30 is referred toas a front side (or active side) of semiconductor substrate 20, and theopposite side is referred to as a backside (or inactive side) ofsemiconductor substrate 20. Also, the front side of semiconductorsubstrate 20 is referred to as the front side (or active side) 10′F ofwafer 10 (device die 10′), and the backside of semiconductor substrate20 is also referred to as the backside (or inactive side) 10′B of devicedie 10′ (wafer 10).

FIG. 2 illustrates a device die 10′ formed by performing a singulationprocess to saw wafer 10 into discrete device dies 10′. In accordancewith some embodiments, the device dies (such as device die 110′ (FIG. 3)used in the subsequent processes may have similar structures as devicedie 10′, and hence the details are not discussed herein.

FIGS. 3 through 22 illustrate the cross-sectional views of intermediatestages in the formation of a package in accordance with some embodimentsof the present disclosure. The corresponding processes are alsoreflected schematically in the process flow shown in FIG. 34. Insubsequent processes, wafers and device dies may have similar structuresas wafer 10 and device die 10′ as shown in FIGS. 1 and 2, respectively.The components in the illustrated wafers and devices may be denoted withlike-numbers in FIGS. 1 and 2, plus number 100, 200, 300, 400, or 500.For example, the through-vias in device die 110′ may be referred to as126, the through-vias in wafer 210 (FIG. 3) may be referred to as 226,and so on. Similarly, the electrical connectors in device die 110′ maybe referred to as 142, and the electrical connectors in wafer 210 may bereferred to as 242, and so on. Also, the substrate in device die 110′may be referred to as 120, and the substrate in wafer 210 may bereferred to as 220, and so on. The properties and the materials of thecomponents may thus be found in the discussion referring to FIGS. 1 and2 by referring to the features having the corresponding numbers.

FIGS. 3 through 8 illustrate the intermediate stages in the bonding ofdevice dies 110′ to wafer 210 and the formation of additional featuresto form packages. Referring to FIG. 3, device dies 110′ are bonded towafer 210. The respective process is illustrated as process 602 in theprocess flow 600 in FIG. 34. Although one device die 110′ isillustrated, a plurality of device dies 110′ are bonded to the devicedies 210′ in wafer 210. The bonding of device dies 110′ to wafer 210 maybe achieved through hybrid bonding. Furthermore, there may be a singleor a plurality of device dies 110′ bonded to the same device die 210′.The plurality of device dies 110′ bonded to the same device die 210′ maybe identical to each other, and the respective bonding structure isreferred to as having a homogenous structure. Alternatively, theplurality of device dies 110′ bonded to the same device die 210′ mayhave structures different from each other, and the respective bondingstructure is referred to as having a heterogeneous structure.

In the hybrid bonding, bond pads 142 are bonded to bond pads 242 throughmetal-to-metal direct bonding. In accordance with some embodiments ofthe present disclosure, the metal-to-metal direct bonding is orcomprises copper-to-copper direct bonding. Furthermore, surfacedielectric layer 134 is bonded to surface dielectric layer 234 throughdielectric-to-dielectric bonding, which may be fusion bonding. Forexample, Si—O—Si bonds may be generated, with Si—O bonds being in afirst one of dielectric layers 134 and 234, and Si atoms being in asecond one of dielectric layers 134 and 234.

To achieve the hybrid bonding, device dies 110′ are first pre-bonded todielectric layer 234 and bond pads 242 by lightly pressing device dies110′ against wafer 210. After all device dies 110′ are pre-bonded, ananneal is performed to cause the inter-diffusion of the metals in bondpads 242 and the corresponding overlying bond pads 142. The annealingtemperature may be higher than about 350° C., and may be in the rangebetween about 350° and about 550° C. in accordance with someembodiments. The annealing time may be in the range between about 1.5hours and about 3.0 hours, and may be in the range between about 1.0hour and about 2.5 hours in accordance with some embodiments. Throughthe hybrid bonding, bond pads 142 are bonded to the corresponding bondpads 242 through direct metal bonding caused by metal inter-diffusion.

In accordance with some embodiments, after the bonding process, abackside grinding is performed to thin device dies 110′, for example, toa thickness between about 15 μm and about 30 μm. Through the thinning ofdevice dies 110′, the aspect ratio of gaps 146 is reduced in order toreduce the difficulty in the gap filling process. After the backsidegrinding, TSVs 126 may be revealed. Alternatively, TSVs 126 are notrevealed at this time, and the backside grinding is stopped when thereis still a thin layer of substrate 120 covering TSVs 126. In accordancewith these embodiments, TSVs 126 may be revealed in the step shown inFIG. 5. In accordance with other embodiments in which the aspect ratioof gaps 146 is not too high, the backside grinding is skipped.

FIG. 4 illustrates the formation of gap-filling materials/layers, whichinclude dielectric layer 150 and the underlying dielectric liner (etchstop layer) 148. The respective process is illustrated as process 604 inthe process flow 600 in FIG. 34. Etch stop layer 148 is formed of adielectric material that has a good adhesion to the sidewalls of devicedies 110′ and the top surfaces of dielectric layer 234 and bond pads242. In accordance with some embodiments of the present disclosure, etchstop layer 148 is formed of a nitride-containing material such assilicon nitride. Etch stop layer 148 may be a conformal layer. Thedeposition may include a conformal deposition method such as AtomicLayer Deposition (ALD) or Chemical Vapor Deposition (CVD).

Dielectric layer 150 is formed of a material different from the materialof etch stop layer 148. In accordance with some embodiments of thepresent disclosure, dielectric layer 150 is formed of silicon oxide,while other dielectric materials such as silicon carbide, siliconoxynitride, silicon oxy-carbo-nitride, PSG, BSG, BPSG, or the like mayalso be used. Dielectric layer 150 may be formed using CVD, High-DensityPlasma Chemical Vapor Deposition (HDPCVD), Flowable CVD, spin-oncoating, or the like. Dielectric layer 150 fully fills the remaininggaps 146 (FIG. 3).

In accordance with alternative embodiments of the present disclosure,instead of forming dielectric layers 148 and 150, device die 110′ isencapsulated by an encapsulant, which may be formed of molding compound,molding underfill, a resin, an epoxy, a polymer, and/or the like.

Referring to FIG. 5, a planarization process such as a CMP process or amechanical grinding process is performed to remove excess portions ofgap-filling layers 148 and 150, so that device dies 110′ are exposed.The planarization process may be continued until TSVs 126 are exposed.The remaining portions of layers 148 and 150 are collectively referredto as (gap-filling) isolation regions 151.

Next, openings (occupied by through-dielectric vias 152) are formed byetching dielectric layer 150 and etch stop layer 148. Through-dielectricvias 152 (also referred to as through-vias) are then formed to fill theopenings, and connect to bond pads 242. The respective process isillustrated as process 606 in the process flow 600 in FIG. 34. Inaccordance with some embodiments of the present disclosure, theformation of through-vias 152 includes performing a plating process suchas an electro-chemical plating process or an electro-less platingprocess. Through-vias 152 may include a metallic material such astungsten, aluminum, copper, or the like, or alloys thereof. A conductivebarrier layer (such as titanium, titanium nitride, tantalum, tantalumnitride, or the like) may also be formed underlying the metallicmaterial. A planarization process such as a CMP process is performed toremove excess portions of the plated metallic material, and theremaining portions of the metallic material form through-vias 152.Through-vias 152 may have substantially straight and vertical sidewalls.Alternatively, through-vias 152 may have a tapered profile, with topwidths slightly greater than the respective bottom widths. In accordancewith alternative embodiments, through-vias 152 are not formed.Accordingly, through-vias 152 are illustrated using dashed lines toindicate that they may be or may not be formed.

In accordance with some embodiments of the present disclosure, as shownin FIG. 6, semiconductor substrate 120 is slightly recessed, for examplethrough an etching process, so that the top portions of TSVs 226protrude out of the recessed semiconductor substrate 120. The respectiveprocess is illustrated as process 608 in the process flow 600 in FIG.34. Isolation regions 151 may be, or may not be, recessed whensemiconductor substrate 120 is recessed.

Next, as shown in FIG. 7, dielectric layer 154 is formed to embed theprotruding portions of TSVs 126 therein. The respective process isillustrated as process 610 in the process flow 600 in FIG. 34. Inaccordance with some embodiments, dielectric layer 154 is formed bydepositing a dielectric layer, which may be formed of silicon oxide,silicon nitride, or the like, and performing a planarization process toremove the excess portions of the dielectric material over TSVs 126, sothat TSVs 126 are revealed. If isolation regions 151 are not recessed inpreceding process, dielectric layer 154 will be limited in the regiondirectly over substrate 120, with the edges 155 of dielectric layer 154being flush with the respective edges of substrate 120. Accordingly,dielectric layer 154 will be between, and contact, the top portions ofisolation regions 151.

Referring to FIG. 8, dielectric layer(s) 156 and redistribution lines(RDLs) 158 are formed. The respective process is illustrated as process612 in the process flow 600 in FIG. 34. Although one dielectric layer156 and one RDL layer are shown as an example, more dielectric layersand RDLs may be formed. In accordance with some embodiments of thepresent disclosure, dielectric layer 156 is formed of asilicon-containing oxide (which may or may not include oxygen). Forexample, dielectric layer 156 may include an oxide such as siliconoxide, a nitride such as silicon nitride, or the like. RDLs 158 may beformed using a damascene process, which includes etching dielectriclayer 156 to form openings, depositing a conductive barrier layer intothe openings, plating a metallic material such as copper or a copperalloy, and performing a planarization to remove the excess portions ofthe metallic material. Alternatively, the formation of dielectric layer156 and RDLs 158 may include forming dielectric layer 156, patterningdielectric layer 156 to form openings, forming a metal seed layer (notshown), forming a patterned plating mask (such as photo resist) to coversome portions of the metal seed layer, while leaving other portionsexposed, plating the RDLs 158, removing the plating mask, and etchingundesirable portions of the metal seed layer.

Bond pads 160 are further formed in dielectric layer 156. The respectiveprocess is also illustrated as process 612 in the process flow 600 inFIG. 34. The top surfaces of bond pads 160 are coplanar with the topsurface of the surface dielectric layer 156. The planarization isachieved through a CMP process or a mechanical grinding process. Bondpads 160 may be formed of or comprise copper, for example. Throughoutthe description, wafer 210 and the overlying structures are collectivelyreferred to as reconstructed wafer 262.

In accordance with some embodiments, wafer 210 is thinned by thinningsemiconductor substrate 120 before the subsequent singulation process.The thinning may be performed through a planarization process such as amechanical grinding process or a CMP process. The thinning may bestopped before TSVs 226 and the corresponding isolation layers areexposed. In accordance with other embodiments, no thinning process isperformed before the subsequent singulation process.

FIG. 8 also illustrates a singulation process performed to singulatereconstructed wafer 262 into discrete packages 262′. The respectiveprocess is illustrated as process 614 in the process flow 600 in FIG.34. The singulation is performed by cutting through scribe lines 261.Packages 262′ are system packages. Wafer 210 is singulated as devicedies 210′.

FIGS. 9 through 12 illustrate the intermediate stages in the bonding ofpackage 262′ to wafer 310 and the formation of additional features toform additional packages. In accordance with some embodiments, theformation process is similar to in FIGS. 3 and 8, wherein wafer 310(FIG. 9) correspond to wafer 210 in FIG. 3, and package 262′ correspondto device die 210′ in FIG. 3. Unless specified otherwise, the likefeatures in FIGS. 9 through 12 may (or may not) be formed using similarmaterials and similar processes as discussed referring to the processesshown in FIGS. 3 through 8.

Referring to FIG. 9, packages 262′ are bonded to wafer 310. Therespective process is illustrated as process 616 in the process flow 600in FIG. 34. Although one package 262′ is illustrated, a plurality ofpackages 262′ are bonded to the device dies 310′ in wafer 310. Thebonding of packages 262′ to wafer 310 may be achieved through hybridbonding, in which both metal-to-metal direct bonding (between bond pads160 and 342) and dielectric-to-dielectric bonding (such as Si—O—Sibonding between surface dielectric layers 156 and 334) are formed.Furthermore, there may be a single or a plurality of package 262′ bondedto the same device die 310′. The plurality of package 262′ bonded to thesame device die 310′ may be identical to, or different from, each otherto form a homogenous or a heterogeneous structure.

Next, as shown in FIG. 10, a gap-filling process is performed toencapsulate packages 262′ in a dielectric material(s). The respectiveprocess is illustrated as process 618 in the process flow 600 in FIG.34. After the dielectric materials are deposited, a planarizationprocess is performed to level the top surfaces of device dies 210′ withthe top surface of the dielectric material. Isolation regions 251 arethus formed, as shown in FIG. 11. In accordance with some embodiments ofthe present disclosure, isolation regions 251 include etch stop layer248 and dielectric region 250 over etch stop layer 248, which may adoptsimilar materials and methods for forming etch stop layer 148 anddielectric region 150, respectively. Alternatively, isolation regions251 are formed of or comprise an encapsulant such as a molding compound,a molding underfill, a resin, an epoxy, or the like.

FIG. 11 further illustrates the formation of through-vias 352. Therespective process is illustrated as process 620 in the process flow 600in FIG. 34. The formation process may be similar to the formation ofthrough-vias 152. In accordance with alternative embodiments,through-vias 252 are not formed. Accordingly, through-vias 252 areillustrated as being dashed to indicate they may be or may not beformed. The substrate 220 in device dies 210′ may then be recessed, sothat the top portions of TSVs 226 protrude over substrate 220. Therespective process is illustrated as process 622 in the process flow 600in FIG. 34. In the meantime, isolation regions 251 may be or may not berecessed. Isolation regions 251 may be or may not be recessed.

In subsequent processes, as shown in FIG. 12, dielectric layers 254 and256, RDLs 258, and bond pads 260 are formed. The respective process isillustrated as process 624 in the process flow 600 in FIG. 34. Theformation processes and the materials of dielectric layers 254 and 256,RDLs 258, and bond pads 260 may be similar to that of dielectric layers154 and 156, RDLs 158, and bond pads 160, respectively, and are notrepeated herein. Throughout the description, wafer 310 and the overlyingstructures are collectively referred to as reconstructed wafer 362.Dielectric layer 254 may be limited directly over substrate 220, or mayextend directly over isolation regions 251, as illustrated in FIG. 12.

In accordance with some embodiments, reconstructed wafer 362 is thinnedby thinning semiconductor substrate 320, for example, through aplanarization process such as a mechanical grinding process or a CMPprocess. The resulting structure is shown in FIG. 13. The thinning maybe stopped before TSVs 326 and the corresponding isolation layers areexposed.

FIG. 13 also illustrates a singulation process performed to singulatereconstructed wafer 362 into discrete packages 362′. The respectiveprocess is illustrated as process 626 in the process flow 600 in FIG.34. The singulation is performed by cutting through scribe lines 361.Packages 362′ are also system packages, which further include pre-formedpackages 262′ therein. In accordance with some embodiments, no moredevice dies are bonded to packages 262′, and packages 262′ may be usedfor the packaging processes as shown in FIGS. 27 through 33. In whichembodiments, there may not be TSVs formed in semiconductor substrate320. In accordance with other embodiments, more device dies are bondedto packages 362′, as shown in FIGS. 14 through 18.

FIGS. 14 through 18 illustrate the intermediate stages in the bonding ofpackage 362′ to wafer 410 and the formation of additional features toform additional packages. The respective process is illustrated asprocess 628 in the process flow 600 in FIG. 34. The bonding of packages362′ to wafer 410 may be achieved through hybrid bonding, in which bothmetal-to-metal direct bonding (between bond pads 260 and 442) anddielectric-to-dielectric bonding (such as Si—O—Si bonding betweensurface dielectric layers 256 and 434) are formed. Unless specifiedotherwise, the like features in FIGS. 14 through 18 may be (or may notbe) formed using similar materials and similar processes as discussedreferring to the processes shown in FIGS. 9 through 13.

Referring to FIG. 14, packages 362′ are bonded to wafer 410. Althoughone package 362′ is illustrated, a plurality of packages 362′ are bondedto the device dies 410′ in wafer 410. Furthermore, there may be a singleor a plurality of package 362′ bonded to the same device die 410′. Theplurality of packages 362′ or device dies (not in packages) bonded tothe same device die 410′ may be identical to, or different from, eachother to form a homogenous or heterogeneous structure. In accordancewith some embodiments of the present disclosure, wafer 410 does notinclude TSVs in semiconductor substrate 420.

Next, as shown in FIG. 15, semiconductor substrate 320 is thinned toreveal TSVs 326. In FIG. 16, a gap-filling process is performed toencapsulate packages 362′ in isolation regions 351, which may includeetch stop layer 348 and dielectric region 350 over etch stop layer 348.Alternatively, isolation regions 351 may include a molding compound, amolding underfill, a resin, an epoxy, or the like. Through-vias 352 maythen be formed in accordance with some embodiments. In accordance withalternative embodiments, through-vias 352 are not formed. Accordingly,through-vias 352 are illustrated as dashed to indicate they may be ormay not be formed.

In subsequent processes, as shown in FIG. 17, semiconductor substrate320 is recessed slightly so that the top portions of TSVs 326 protrudeout of semiconductor substrate 320. Next, as shown in FIG. 18,dielectric layers 354 and 356, RDLs 358, and bond pads 360 are formed.The formation processes and the materials of dielectric layers 354 and356, RDLs 358, and bond pads 360 may be similar to that of dielectriclayers 154 and 156, RDLs 158, and bond pads 160, respectively, and arenot repeated herein. Throughout the description, wafer 410 and theoverlying structures are collectively referred to as reconstructed wafer462. In accordance with some embodiments, reconstructed wafer 462 isthinned by thinning semiconductor substrate 420 through a planarizationprocess.

FIG. 18 also illustrates a singulation process performed to singulatereconstructed wafer 462 into discrete packages 462′. The singulation isperformed by cutting through scribe lines 461. Throughout thedescription, packages 462′ are alternatively referred to as SoICpackages 462′. Packages 462′ include pre-formed packages 362′, whichfurther include pre-formed packages 262′ therein. In accordance withsome embodiments, no more device dies are further bonded to packages462′, and the resulting package may be used for the packaging processesas shown in FIGS. 27 through 33. In accordance with other embodiments,more device dies are bonded, as shown in FIGS. 19 through 22.

FIGS. 19 through 22 illustrate the intermediate stages in the bonding ofpackage 462′ to wafer 510 and the formation of additional features toform additional packages. The respective process is illustrated asprocess 630 in the process flow 600 in FIG. 34. The bonding of packages462′ to wafer 510 may be achieved through hybrid bonding, in which bothmetal-to-metal direct bonding (between bond pads 360 and 542) anddielectric-to-dielectric bonding (such as Si—O—Si bonding betweensurface dielectric layers 356 and 534) are formed. Unless specifiedotherwise, the like features in FIGS. 19 through 22 may be (or may notbe) formed using similar materials and similar processes as discussedreferring to the processes shown in FIGS. 14 through 18.

Referring to FIG. 19, packages 462′ are bonded to wafer 510. Althoughone package 462′ is illustrated, a plurality of packages 462′ are bondedto the device dies 510′ in wafer 510. Furthermore, there may be a singleor a plurality of package 462′ bonded to the same device die 510′ toform a homogenous structure or a heterogeneous structure.

Next, as shown in FIG. 20, semiconductor substrate 420 is furtherthinned, and packages 462′ are encapsulated in a dielectric material(s)to form gap-filling regions 451, which may include etch stop layer 448and dielectric region 450 over etch stop layer 448, or may include anencapsulant such as a molding compound, a molding underfill, a resin, anepoxy, or the like.

In subsequent processes, as shown in FIG. 21, semiconductor substrate520 is recessed slightly so that TSVs 526 protrude out of semiconductorsubstrate 520. Next, as shown in FIG. 22, dielectric layers 554 and 556,RDLs 558, and bond pads 560 are formed. The formation processes and thematerials of dielectric layers 554 and 556, RDLs 558, and bond pads 560may be similar to that of dielectric layers 154 and 156, RDLs 158, andbond pads 160, respectively, and are not repeated herein. Throughout thedescription, wafer 510 and the overlying structures are collectivelyreferred to as reconstructed wafer 562.

FIG. 22 also illustrates a singulation process performed to singulatereconstructed wafer 562 into discrete packages 562′. The singulation isperformed by cutting through scribe lines 561. Throughout thedescription, packages 562′ are alternatively referred to as SoICpackages 562′. Packages 562′ include pre-formed packages 462′, whichfurther include pre-formed packages 362′ and 262′ therein. In accordancewith some embodiments, the bonding of further device dies may bestopped, and the resulting package may be used for the packagingprocesses as shown in FIGS. 27 through 33. In accordance with otherembodiments, more device dies are bonded.

In accordance with some embodiments of the present disclosure, the frontsurface 110F of device die 110′ and the front surface 210F of device die210′ are bonded to each other. The backside of device die 110′ faces thefront side of device die 310′, as indicated by interface 110B/310F. Thefront side of device die 410′ faces the backside of device die 210′, asindicated by interface 410F/210B. The front side of device die 510′faces the backside of device die 310′, as indicated by interface510F/310B. This bonding scheme is caused by starting from die 110′, andbonding dies alternatingly on the front side and the back side of die110′. Such a way of bonding has an advantageous feature since the bondedwafer in each bonding step (such as shown in FIGS. 3, 9, 14, and 19) maybe used as the carrier for the formation of the respective packages, sothat no additional carriers are needed. In accordance with someembodiments of the present disclosure, instead of bonding to the frontside and the back side of die 110′ alternatingly, other bonding schemesmay be use.

In the embodiments shown in FIGS. 3 through 22, the bonding pads for theexternal connection of package 562′ are formed on the device die 510′,which is the last bonded die. In accordance with alternativeembodiments, the bonding pads for the external connection of package562′ are formed on the device die 410′, which is bonded before the lastdie is bonded. The corresponding formation process is illustrated inFIGS. 23 through 26. Unless specified otherwise, the materials and theformation processes of the components in these embodiments areessentially the same as the like components, which are denoted by likereference numerals in the preceding embodiments shown in FIGS. 3 through22. The details regarding the formation process and the materials of thecomponents shown in FIGS. 23 through 26 may thus be found in thediscussion of the preceding embodiments.

FIG. 23 illustrates package 462′, which is essentially the same as thepackage 462′ shown in FIG. 18, except in FIG. 23, TSVs 426 are formed indevice die 410′. Packages 462′ are bonded to wafer 510 through hybridbonding, with bonding pads 360 bonded to bond pads 542, and dielectriclayers 356 and 534 bonded through fusion bonding. Wafer 510 is free fromTSVs extending into the corresponding semiconductor substrate 520.

Next, as shown in FIG. 24, semiconductor substrate 420 is thinned, andpackages 462′ are encapsulated in a dielectric material(s) to formisolation regions 451, which may include etch stop layer 448 anddielectric region 450 over etch stop layer 448, or may include anencapsulant such as a molding compound, a molding underfill, a resin, anepoxy, or the like.

In subsequent processes, as shown in FIG. 25, semiconductor substrate420 is recessed slightly so that TSVs 426 protrude out of semiconductorsubstrate 420. Isolation regions 451 may be, or may not be, recessed.Next, as shown in FIG. 26, dielectric layers 454 and 456, RDLs 458, andbond pads 460 are formed. Through-vias 552 may be (or may not be)formed. Throughout the description, wafer 510 and the overlyingstructures are collectively referred to as reconstructed wafer 562. Inaccordance with some embodiments, reconstructed wafer 562 is thinned bythinning semiconductor substrate 520 through a planarization process.

FIG. 26 also illustrates a singulation process performed to singulatereconstructed wafer 562 into discrete packages 562′. The singulation isperformed by cutting through scribe lines 561. In accordance with someembodiments, the bonding of further device dies may be stopped, and theresulting package may be used for the packaging processes as shown inFIGS. 27 through 33. In accordance with other embodiments, more devicedies are bonded.

FIGS. 27 through 31 illustrate the example applications of IntegratedFan-Out (InFO) packages 80A, 80B, 80C, 80D, and 80E. The packagesinclude 62′, which may be package 562′, package 462′, or package 362′(FIG. 22 or 26) in accordance with some embodiments. As shown in FIG.27, package 80A is formed. Package 80A includes package 62′ encapsulatedin encapsulant 70, which may be, or may comprise, a molding compound, amolding underfill, a resin, an epoxy, or the like. Through-vias 72 areformed in encapsulant 70 to interconnect the conductive features on theopposite sides of encapsulant 70. FIG. 28 illustrates InFO package 80B,which is similar to the package 80A shown in FIG. 27, except nothrough-vias are formed in encapsulant 70, and no electrical connectorsare formed underlying encapsulant 70. FIG. 29 illustrates InFO package80C, which is similar to the package 80B shown in FIG. 28, except devicedie 82 is bonded to package 62′ through flip-chip bonding. FIG. 30illustrates InFO package 80D, which is similar to the package 80A shownin FIG. 27, except two device dies 82 are bonded to package 62′ andthrough-vias 72 through flip chip bonding. FIG. 31 illustrates package80E including two tiers of packages 62′ (including 62A′, 62B′, and62C′), which are encapsulated in encapsulant 70A and 70B.

FIGS. 32 and 33 illustrate the example applications ofChip-on-Wafer-on-Substrate (CoWoS) packages 80F and 80G, respectively,which further include packages 62′. Packages 62′ may be package 562′,package 462′, or package 362′ (FIG. 22 or 26) in accordance with someembodiments, as discussed in preceding embodiments. As shown in FIG. 32,package 80F includes package 62′ and memory stacks 84 encapsulated inencapsulant 85, which may be or may comprise a molding compound, amolding underfill, a resin, an epoxy, or the like. Interposer 86 isunderlying and bonded to package 62′ and memory stacks 84. Packagesubstrate 88 is further underlying and bonded to interposer 86.Surface-Mount Devices (SMDs) 90, which may be or include passive devicessuch as capacitors, inductors, or the like, are bonded to packagesubstrate 88. Metal cap 92 is placed on package substrate 88, withThermal Interface Material (TIM) 93 joining metal cap 92 to package 62′and memory stacks 84. FIG. 33 illustrates a package 80G similar to theembodiment shown in FIG. 32, except that the package 62′ show in FIG. 32is replaced with package 80, which may be any of the InFO packages 80A,80B, 80C, 80D, and 80E as shown in FIGS. 27 through 31.

As shown in FIGS. 22 and 26 and the corresponding formation processes,device die 110′ may be in the center of the package. In accordance withsome embodiments of the present disclosure, device dies 210′, 310′, 410′and 510′ may be bonded starting from the center device die 110′, and thesubsequently bonded devices may be bonded from alternating sides ofdevice die 110′. For example, device die 210′ may be bonded to the frontside of device die 110′, device die 310′ may then be bonded to thebackside of device die 110′, device die 410′ may then be bonded to thefront side of device die 110′ again, and device die 510′ may be bondedto the backside of device die 110′ again. The center die 110′ may be acomputing die, and other application dies are bonded on the oppositeside of center die 110′. Also, the outer dies of the packages may beincreasingly larger than the corresponding inner dies. Such a scheme ofallocation has some advantageous features. For example, the computingdie, being in the center, has short distances from all other dies, andthe performance of the package may be improved without significantbottleneck in the accessing speed. Also, through the alternating bondingscheme, it is possible to form through-vias 152 directly interconnectingdevice dies 210′ and 310′, and through-vias 352 directly interconnectingdevice dies 310′ and 410′. Through-vias 552 may also be used tointerconnect device dies 410′ and 510′ through bond pads 542 (FIG. 26)and the underlying RDLs in device dies 510′. The direct connectionbetween the dies significantly improves the speed of the resultingpackage. Also, through the alternating bonding scheme, each of thewafers may be used as a carrier so that no additional carrier is needed.

The embodiments of the present disclosure have some advantageousfeatures. By stacking dies, the footprint of the package is reduced. Bymaking the inner dies smaller than the outer dies, direct connectionsmay be formed between each pair of dies. Since each of the dies isthinned, the thickness of the package is small. Due to the directconnection and the small distance between the dies, the signaltransmission performance is improved.

In accordance with some embodiments of the present disclosure, a packageincludes a first device die; a second device die bonded to the firstdevice die, wherein the second device die is larger than the firstdevice die, and wherein first bond pads of the first device die arebonded to second bond pads of the second device die throughmetal-to-metal bonding, and a first surface dielectric layer of thefirst device die is bonded to a second surface dielectric layer of thesecond device die through fusion bonding; a first isolation regionencapsulating the first device die therein, wherein the first devicedie, the second device die, and the first isolation region form parts ofa first package; a third device die bonded to the first package, whereinthe third device die is larger than the first package, and wherein thirdbond pads of the third device die are bonded to fourth bond pads of thefirst package through metal-to-metal bonding, and a third surfacedielectric layer of the third device die is bonded to a fourth surfacedielectric layer of the first package through fusion bonding; and asecond isolation region encapsulating the first package therein, whereinthe first package, the third device die, and the second isolation regionform parts of a second package. In an embodiment, the package furthercomprises a first through-via penetrating through the first isolationregion, wherein the first through-via direct connects the second devicedie to the third device die. In an embodiment, the second device die andthe third device die are on a front side and a backside, respectively,of the first device die. In an embodiment, the package further comprisesa fourth device die bonded to the second package, wherein the fourthdevice die is larger than the second package, and wherein fifth bondpads of the fourth device die are bonded to sixth bond pads of thesecond package through metal-to-metal bonding, and a fifth surfacedielectric layer of the fourth device die is bonded to a sixth surfacedielectric layer of the second package through fusion bonding; and athird isolation region encapsulating the second package therein, whereinthe second package, the fourth device die, and the third isolationregion form parts of a third package. In an embodiment, the packagefurther comprises a fifth device die bonded to the third package,wherein the fifth device die is larger than the third package, andwherein seventh bond pads of the fifth device die are bonded to eighthbond pads of the third package through metal-to-metal bonding, and aseventh surface dielectric layer of the fifth device die is bonded to aneighth surface dielectric layer of the third package through fusionbonding; and a fourth isolation region encapsulating the third packagetherein, wherein the third package, the fifth device die, and the fourthisolation region form parts of a fourth package. In an embodiment, thepackage further comprises an encapsulant encapsulating the fourthpackage therein; and redistribution lines formed over the encapsulantand the fourth package, wherein the redistribution lines extendlaterally beyond opposite edges of the fourth package. In an embodiment,the package further comprises a second through-via penetrating throughthe second isolation region, wherein the second through-viainterconnects the third device die and the fourth device dieelectrically. In an embodiment, the first isolation region comprises asilicon nitride liner contacting both of the first device die and thesecond device die; and an oxide region on the silicon nitride liner. Inan embodiment, the fourth surface dielectric layer of the first packagehave opposite edges flush with corresponding opposite edges of asemiconductor substrate of the second device die.

In accordance with some embodiments of the present disclosure, a packageincludes a first device die; a second device die bonded to a front sideof the first device die; a first gap-filling material encircling thefirst device die to form a first package along with the first device dieand the second device die, wherein edges of the first gap-fillingmaterial are flush with respective edges of the second device die; athird device die bonded to the first package, wherein the third devicedie is on a backside of the first device die; and a second gap-fillingmaterial encircling the first package to form a second package alongwith the first package and the third device die, wherein edges of thesecond gap-filling material are flush with respective edges of the thirddevice die. In an embodiment, the first device die is bonded to thesecond device die through a first hybrid bonding comprisingmetal-to-metal direct bonding and fusion bonding, and the third devicedie is bonded to the first package through a second hybrid bonding. Inan embodiment, the package further comprises a first through-viapenetrating through the first gap-filling material; and a secondthrough-via penetrating through the second gap-filling material. In anembodiment, the package further comprises a fourth device die bonded tothe second package, wherein the fourth device die is on a backside ofthe second device die; and a third gap-filling material encircling thesecond package to form a third package along with the second package andthe fourth device die, wherein edges of the third gap-filling materialare flush with respective edges of the fourth device die. In anembodiment, the package further comprises a first through-viapenetrating through the first gap-filling material; a second through-viapenetrating through the second gap-filling material; and a thirdthrough-via penetrating through the third gap-filling material. In anembodiment, the first through-via directly connects the second devicedie to the third device die, and the second through-via directlyconnects the third device die to the fourth device die.

In accordance with some embodiments of the present disclosure, methodincludes bonding a first device die onto a second device die of a firstwafer; encapsulating the first device die in a first gap-fillingmaterial; forming first bond pads on a backside of a first semiconductorsubstrate of the second device die, wherein the first bond pads areelectrically connected to first through-vias penetrating through thefirst semiconductor substrate; singulating the first wafer and the firstgap-filling material to form a first package, wherein the first packagecomprises the first device die and the second device die; bonding thefirst package onto a third device die of a second wafer; encapsulatingthe first package in a second gap-filling material; forming second bondpads on a backside of a second semiconductor substrate of the thirddevice die, wherein the second bond pads are electrically connected tosecond through-vias penetrating through the second semiconductorsubstrate; and singulating the second wafer and the second gap-fillingmaterial to form a second package, wherein the second package comprisesthe first package and the third device die. In an embodiment, the firstdevice die is bonded to the second device die through hybrid bonding. Inan embodiment, the method further comprises forming a first through-viapenetrating through the first gap-filling material, wherein the firstthrough-via directly connects the first device die to the second devicedie. In an embodiment, the method further comprises bonding the secondpackage onto a fourth device die of a third wafer; encapsulating thesecond package in a third gap-filling material; forming third bond padson a backside of a third semiconductor substrate of the fourth devicedie, wherein the third bond pads are electrically connected to thirdthrough-vias penetrating through the third semiconductor substrate; andsingulating the third wafer and the third gap-filling material to form athird package, wherein the third package comprises the second packageand the fourth device die. In an embodiment, the forming the first bondpads comprises planarizing the backside of the first semiconductorsubstrate of the second device die to reveal TSVs; etching the firstsemiconductor substrate to allow portions of the TSVs to protrude beyondthe first semiconductor substrate; forming a dielectric layer toencapsulating the portions of the TSVs; and forming the first bond padsto electrically connect to the TSVs.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A package comprising: a first device die; asecond device die bonded to the first device die, wherein the seconddevice die is larger than the first device die, and wherein first bondpads of the first device die are bonded to, and are in physical contactwith, second bond pads of the second device die through metal-to-metalbonding, and a first surface dielectric layer of the first device die isbonded to, and is in physical contact with, a second surface dielectriclayer of the second device die through fusion bonding; a first isolationregion encapsulating the first device die therein, wherein the firstdevice die, the second device die, and the first isolation region formparts of a first package; a third device die bonded to the firstpackage, wherein the third device die is larger than the first package,and wherein third bond pads of the third device die are bonded to, andare in physical contact with, fourth bond pads of the first packagethrough metal-to-metal bonding, and a third surface dielectric layer ofthe third device die is bonded to, and is in physical contact with, afourth surface dielectric layer of the first package through fusionbonding; and a second isolation region encapsulating the first packagetherein, wherein the first package, the third device die, and the secondisolation region form parts of a second package.
 2. The package of claim1 further comprising a first through-via penetrating through the firstisolation region, wherein the first through-via direct connects thesecond device die to the third device die.
 3. The package of claim 1,wherein the second device die and the third device die are on a frontside and a backside, respectively, of the first device die.
 4. Thepackage of claim 1 further comprising: a fourth device die bonded to thesecond package, wherein the fourth device die is larger than the secondpackage, and wherein fifth bond pads of the fourth device die are bondedto sixth bond pads of the second package through metal-to-metal bonding,and a fifth surface dielectric layer of the fourth device die is bondedto a sixth surface dielectric layer of the second package through fusionbonding; and a third isolation region encapsulating the second packagetherein, wherein the second package, the fourth device die, and thethird isolation region form parts of a third package.
 5. The package ofclaim 4 further comprising: a fifth device die bonded to the thirdpackage, wherein the fifth device die is larger than the third package,and wherein seventh bond pads of the fifth device die are bonded toeighth bond pads of the third package through metal-to-metal bonding,and a seventh surface dielectric layer of the fifth device die is bondedto an eighth surface dielectric layer of the third package throughfusion bonding; and a fourth isolation region encapsulating the thirdpackage therein, wherein the third package, the fifth device die, andthe fourth isolation region form parts of a fourth package.
 6. Thepackage of claim 5 further comprising: an encapsulant encapsulating thefourth package therein; and redistribution lines formed over theencapsulant and the fourth package, wherein the redistribution linesextend laterally beyond opposite edges of the fourth package.
 7. Thepackage of claim 4 further comprising a second through-via penetratingthrough the second isolation region, wherein the second through-viainterconnects the third device die and the fourth device dieelectrically.
 8. The package of claim 1, wherein the first isolationregion comprises: a silicon nitride liner contacting both of the firstdevice die and the second device die; and an oxide region on the siliconnitride liner.
 9. The package of claim 1, wherein the fourth surfacedielectric layer of the first package have opposite edges flush withcorresponding opposite edges of a semiconductor substrate of the seconddevice die.
 10. A package comprising: a first device die; a seconddevice die bonded to a front side of the first device die, wherein thefirst device die and the second device die contact each other to form afirst interface; a first gap-filling material encircling the firstdevice die to form a first package along with the first device die andthe second device die; a third device die bonded to the first package,wherein the third device die is on a backside of the first device die;and a second gap-filling material encircling the first package to form asecond package along with the first package and the third device die,wherein a first edge of the first gap-filling material contacts a secondedge of the second gap-filling material to form a second interfaceperpendicular to the first interface, and the second interface is flushwith a respective edge of the second device die.
 11. The package ofclaim 10, wherein a first dielectric layer in the first device die isphysically joined to a second dielectric layer in the second device die,and a first bond pad in the first device die is physically joined to asecond bond pad in the second device die.
 12. The package of claim 10further comprising: a first through-via penetrating through the firstgap-filling material; and a second through-via penetrating through thesecond gap-filling material.
 13. The package of claim 10 furthercomprising: a fourth device die bonded to the second package, whereinthe fourth device die is on a backside of the second device die; and athird gap-filling material encircling the second package to form a thirdpackage along with the second package and the fourth device die, whereina third edge of the second gap-filling material contacts a fourth edgeof third gap-filling material to form a third interface perpendicular tothe first interface, and the second interface is vertically aligned to arespective edge of the third device die.
 14. The package of claim 13further comprising: a first through-via penetrating through the firstgap-filling material; a second through-via penetrating through thesecond gap-filling material; and a third through-via penetrating throughthe third gap-filling material.
 15. The package of claim 14, wherein thefirst through-via directly connects the second device die to the thirddevice die, and the second through-via directly connects the thirddevice die to the fourth device die.
 16. A package comprising: a firstdevice die comprising: a semiconductor substrate; and athrough-substrate via penetrating through the semiconductor substrate; asecond device die overlying and bonded to the first device die, whereina first dielectric layer in the first device die is physically joined toa second dielectric layer in the second device die, and a first bond padin the first device die is physically joined to a second bond pad in thesecond device die; a third device die underlying and bonded to the firstdevice die; a first gap-filling material encircling the first devicedie, wherein the first gap-filling material is overlapped by the seconddevice die and overlapping the third device die; and a firstthrough-dielectric via penetrating through the first gap-fillingmaterial, wherein the first through-dielectric via electricallyinterconnects the second device die and the third device die.
 17. Thepackage of claim 16 further comprising a second gap-filling materialencircling the first device die and the first gap-filling material,wherein the first gap-filling material and the second gap-fillingmaterial form a vertical interface.
 18. The package of claim 17, whereinedges of the first gap-filling material are flush with respective edgesof the second device die, and wherein edges of the second gap-fillingmaterial are flush with respective edges of the third device die. 19.The package of claim 17 further comprising a second through-dielectricvia penetrating through the second gap-filling material, wherein a topend of the second through-dielectric via is higher than a top surface ofthe second device die, and a bottom end of the second through-dielectricvia is in physical contact with the third device die.
 20. The package ofclaim 16 further comprising a redistribution structure between, andbonding to, the first device die and the third device die, wherein theredistribution structure comprises a plurality of dielectric layers andconductive features in the plurality of dielectric layers, and whereinedges of the dielectric layers are flush with corresponding edges of thesecond device die, and are laterally recessed from corresponding edgesof the third device die.